The present disclosure relates to a shortage voltage trip device of molded case circuit breaker.
Molded case circuit breakers are, for example, electronic devices which switch power circuit having a relatively low voltage of several hundred volts or less and perform a trip operation for automatically breaking the power circuit when abnormal current flows into the power circuit. Such a molded case circuit breaker includes a contact part for switching a power circuit, a handle for manually switching the contact part, a switching mechanism providing a driving force for switching the contact part, a trip bar for triggering so that the switching mechanism is tripped, a trip mechanism for detecting abnormal current such as overcurrent or short-circuit current on the power circuit to operate the trip bar, and an arc extinguishing mechanism for extinguishing an arc generated at the contact part during the trip operation.
The molded case circuit breaker may further include a shortage voltage trip device which interrupts the introduction of current into the circuit of the molded case circuit breaker when a voltage less than a rated voltage is applied and displays the interruption of the current.
FIG. 1 is a perspective view illustrating a shortage voltage trip device of a molded case circuit breaker according to a related art. FIG. 2 is an exploded perspective view of a tip driving mechanism constituting the shortage voltage trip device of the molded case circuit breaker according to the related art.
Referring to FIG. 1, various components for operating a switching mechanism of a molded case circuit breaker to open a circuit when a voltage less than a rated voltage is applied into a circuit may be installed within a casing 10 of a shortage voltage trip device 1 (hereinafter, referred to as a “trip device”) of the molded case circuit breaker according to the related art.
In more detail, a printed circuit board (PCB) is disposed within the casing 10. The PCB 11 is connected to a line-side terminal 13 and a power source-side terminal 15 to calculate a voltage applied into the circuit, thereby determining whether the applied voltage is less than the rated voltage.
Also, a trip mechanism for operating the molded case circuit breaker to break the circuit when the voltage applied into the circuit is less than the rated voltage is installed within the casing 10. The trip mechanism includes a trip lever 17, a reset button 19, and a trip driving part 20.
The trip lever 17 is rotatably installed within the casing 10. The trip lever 17 operates the switching mechanism of the molded case circuit breaker to break the circuit when the voltage less than the rated voltage is applied into the circuit. That is, substantially, the trip lever 17 is rotated between a trip position for closing the circuit and a normal position for opening the circuit.
The reset button 19 protrudes to the outside of the casing 10 by being linked with the rotation of the trip lever 17 when the trip lever 17 is rotated and then disposed at the trip position. Thus, a user may recognize a trip state through the reset button 19 protruding to the outside of the casing 10. Also, when the transmission of a driving force from the trip driving part 20 into the trip lever 17 is finished, i.e., in a state where the driving current applied into a coil 23 is interrupted, the reset button 19 provides a driving force for rotating the trip lever 17 so that the trip lever 17 is disposed from the trip position to the normal position. That is, when the user presses and pushes the reset button in a direction in which the reset button 19 is inserted into the casing 10, the trip lever 17 is rotated by being linked with the insertion of the reset button 19 to rotate the trip lever 17 from the trip position to the normal position.
The trip driving part 20 may provide a driving force for rotating the trip lever 17 when the voltage applied into the circuit is less than the rated voltage.
Referring to FIG. 2, the trip driving part 20 includes a moving coil 21, a coil 23, a bobbin 27, a core spring 25, and a yoke 29.
In detail, the moving core 21 rotates the trip lever 17 to locate the trip lever 17 at the trip position. Also, the coil 23 surrounds the moving core 21. When the voltage less than the rated voltage is applied into the circuit, the coil 23 receives driving current from the PCB 11. When the driving current is applied into the coil 23, an electromagnetic force is generated. Thus, the moving core 21 is moved to rotate the trip lever 17 so that the trip lever 17 is disposed at the trip position. The bobbin 25 has a cylindrical shape. The coil 23 is wound around an outer surface of the bobbin 25. When the driving current applied into the coil 23 is interrupted, the core spring 27 provides an elastic force into the moving core 21 to move the moving core 21 to its original position. For this, the core spring 27 is pressed by the moving core 21 moved by the electromagnetic force generated in the coil 23 due to the apply of the driving current. The yoke 29 amplifies the electromagnetic force generated in the coil 23.
In the trip device 1, the PCB 11 determines whether a voltage applied into the circuit is less than the rated voltage. When the PCB 11 determines that the voltage applied into the circuit is less than the rated voltage, the PCB 11 applies driving current into the trip driving part 20. Thus, the moving core 21 is moved to rotate the trip lever 17 so that the trip lever 17 is disposed from the normal position to the trip position. Here, the core spring 27 is pressed by the moving core 21.
Also, when the trip lever 17 is rotated and then disposed at the trip position, the switching mechanism of the circuit breaker is operated to open the circuit. Also, since the reset button 19 is linked with the rotation of the trip lever 17 to protrude to the outside of the casing 10, the user may recognize the trip state.
When the voltage applied into the circuit is increased to excess the related voltage, the PCB 11 determines that the voltage applied into the circuit excesses the related voltage. Then, the PCB 11 interrupts the driving current applied into the trip driving part 20. Thus, the moving core 21 returns to its original position by the elastic force of the core spring 27. In this state, when the user presses the reset button 19 to insert the reset button 19 into the casing 10, the trip lever 17 is rotated by being linked with the movement of the reset button 19 so that the trip lever 17 is disposed from the trip position to the normal position. Also, after the trip lever 17 is disposed at the normal position, the user operates the switching mechanism of the circuit breaker to close the circuit.
However, the shortage voltage trip device of the molded case circuit breaker according to the related art has following limitations.
First, in the related art, to close the circuit tripped by the trip device 1, the trip device 1 should be operated (i.e., the reset button 19 should be manipulated) and the circuit breaker should be operated (i.e., the switching mechanism should be manipulated). Thus, the user should perform operations in two stages to close the circuit.
Also, in the related art, the driving current for the trip operation of the trip device 1 is substantially transmitted into the trip driving part 20 through the PCB 11. Thus, when a voltage applied into the circuit is zero voltage, the driving current is not applied into the trip driving part 20 from the PCB 11. For example, when a voltage applied into the circuit ranges from about 0% to about 15% of the rated voltage, the trip operation is not substantially performed.
Also, in the related art, the PCB 11 determines whether the voltage applied into the circuit is less than the rated voltage. Thus, a device for comparing voltages to each other should be provided on the PCB 11. As a result, as the PCB 11 is increased in price, manufacturing costs of the product may be substantially increased.